TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker or making a Paypal contribution here: paypal.me/SupportTMC

Question about traction control on P85D and how regen behaves on ice

Discussion in 'Model S: Driving Dynamics' started by Andyw2100, Jan 23, 2015.

  1. Andyw2100

    Andyw2100 Well-Known Member

    Joined:
    Oct 22, 2014
    Messages:
    5,387
    Location:
    Ithaca, NY
    About a week ago I had my first experience sliding in my P85D.

    It was snowing pretty heavily, and the roads were quite slick. I was slowing to turn off of a main road, on a slight downhill, using regenerative braking. I was probably only doing 15-20 MPH, if that, at the point when I started my turn. I felt the back end start to come around, and I instinctively and incorrectly completely let off the accelerator, which of course would possibly have only served to increase the regenerative braking, which would not have helped at all in this situation. It would have been better, of course, assuming I could have done it, to try to find the point at which the car was neither braking nor accelerating.

    In any case, since I was going pretty slowly, I only slid for a couple of seconds, and I felt like the front end gained traction and pulled me out of the slide, and it really wasn't a big deal at all. But what I'm wondering is if the P85Ds traction control is smart enough to have recognized the slide and to have stopped the regenerative braking on its own, and if that might have contributed to how quickly I came out of the slide.

    It would be nice to think that next time I'd be able to react better, but decades of driving ICE vehicles and instinctively letting off the accelerator when sliding on ice is not something I'm likely going to overcome easily, especially since I'm going to still be driving my ICE some of the time. I'd like to know if the P85D is smart enough to compensate for me not being able to make the correct adjustment for how to drive using regenerative braking when sliding on ice.

    I do know, from reading these forums, that when driving in slippery conditions we should set regenerative braking to low. I had not done that.

    Thanks!
     
  2. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

    Joined:
    Mar 8, 2012
    Messages:
    12,752
    Location:
    Texas
    Yes, the Model S has stability control. Also you didn't mention what tires you had on--performance summers are not acceptable for winter conditions, and many all-seasons are just barely passable when brand new. FWIW, I've yet to have a problem on slippery days using standard regen.
     
  3. Andyw2100

    Andyw2100 Well-Known Member

    Joined:
    Oct 22, 2014
    Messages:
    5,387
    Location:
    Ithaca, NY
    I have the Tesla winter wheel package, so that's the Pirelli Sottozero IIs. And yes, I know the P85D has stability control. What I'm asking is if the traction control includes cutting off regenerative braking completely when sliding on ice the way I was.

    Thanks.
     
  4. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

    Joined:
    Mar 8, 2012
    Messages:
    12,752
    Location:
    Texas
    Haven't had any ice to drive on this winter, but last winter it modulated the brakes so that I didn't lose control. As I recall it doesn't remove regen completely. Traction control is straight line stopping, vehicle stability control kicks in on turns so you would have a mixture of TC and VSC.
     
  5. kseitzberg

    kseitzberg Member

    Joined:
    Dec 21, 2012
    Messages:
    86
    Location:
    Denmark
    Yes, when driving on very slippery roads, the regen (when set on standard), can cause the car to brake on the rear wheels. However only for a very short period, whereafter the TC kicks in and reduces the regen.

    Back in november I planned a driving course for 16 TMS in Denmark, where we took the cars to a winter driving facility to learn how it handles in winter weather, even though I tried it last winter. The conclusion were that during winter - keep regen on standard, unless you are driving on very slippery or icy roads. If very icy, change regen to low, and car handles absolutely perfect. Actually it was one of the most predictable cars that the testing facility had ever seen on the track (called FDM in Denmark). Normally FDM is very sceptical with EV's, but they loved how the TMS handles during winter conditions.

    So to conclude the learnings: Install good winter tyres, and drive safely. If icy conditions occur, change regen to LOW. Do not drive faster than the physics of the car/conditions allows.
     
  6. Andyw2100

    Andyw2100 Well-Known Member

    Joined:
    Oct 22, 2014
    Messages:
    5,387
    Location:
    Ithaca, NY
    Thanks for the answers. It sounds like the car probably reduced the regenerative braking pretty quickly once it started sliding.

    I appreciate the responses.
     

Share This Page